The invention relates to machines or rigs for drilling holes, e.g. blast holes for driving drifts of medium to small section with the employment of the blasting method.
There are known gantry-type drilling rigs with hydraulically operated drilling booms, intended for drilling blast holes and operable in underground drifts provided with rail tracks.
The most similar in structure to the drilling rig of the present invention is the one marketed by Ingersoll-Rand World Trade Limited and disclosed in the U.S. Pat. No. 3,334,849, Cl. 248-13, patented in 1967.
The drilling rig disclosed in this patent includes a frame and at least one drilling boom pivotally supported by the frame and adapted to support a drilling tool.
At each side of the frame there are mounted interconnected supports or legs, at least one of these legs being pivotally connected with the frame.
The known drilling rig includes also a hydraulic mechanism for actuating the legs pivotally connected with the frame, whereby the rig can be adjusted for transporting purposes from a drilling position in which the frame is supported by the legs bearing upon the ground of the drift.
One of the legs has an arm-like extension projecting beyond the pivot pin about which the leg is mounted on the frame. This arm-like extension is connected with the frame by means of a hydraulic cylinder which effects swinging of the leg about its pivot pin.
In the abovedescribed known drilling rig another leg has arms mounted on the frame for pivoting about a vertical axis, whereby the rig can be adjusted for transporting purposes.
The provisions for varying the overall dimensions of a drilling machine at transportation and at drilling offer certain advantages.
The Ingersoll-Rand World Trade Limited has developed a gantry type drilling rig supported on rails, wherein there has been utilized the abovedescribed structural method of varying the overall dimensions of the rig by folding its members on the frame for transporting purposes.
The gantry type drilling ring incorporates a housing supporting thereon hydraulically actuated drilling booms, the housing being supported on rails by means of two pairs of wheels. The rig further incorporates jacks by means of which the housing of the rig together with the drilling booms can be lifted to the roof of the drift, so that load-carrying and like machines and vehicles should be able to pass under the rig.
However, the abovedescribed known rig is not free from disadvantages.
One of the disadvantages arises from the housing of the rig being situated relatively high above the ground of the drift, which increases the total height of the rig in the gantry position and complicates the operation of the rig in relatively small-height drifts, making it virtually impossible to pass load-carrying and handling means of a considerable height under the gantry.
The relatively high position of the housing is explained by the kinematics of folding the legs of the rig, which means that the pivot pins of the arms should be above the wheels of the rig, so that the legs should be lifted higher than the wheels and ensure sufficient ground clearance at transportation. Furthermore, the abovedescribed rig cannot be transported without disassembling along single-track drifts of relatively small cross-sectional area wherein the central axis of the track is considerably displaced from the central axis of the drift.
The operator's place on the known drilling rigs in the drilling position is also relatively high above the ground of the drift, which involves additional difficulties in operating the rig.
Although the gantry type drilling rig marketed by the Ingersoll-Rand World Trade Limited is more vibration-stable than the structures that had preceded this rig, however, it is not completely free from the vibration hazard.